This invention relates to gigahertz electronic devices containing elements composed of polyimides selected for their high polyimide equivalent weight.
U.S. Pat. Nos. 5,386,002, 3,758,434, 5,750,641, 5,969,088, 6,084,053 and 5,145,942 describes polyimides, some including polyimides derived from a fluorenyl diamine.
Briefly, the present invention provides an element of a gigahertz electronic device, i.e. a device for use with radiation or electronic signals in the 1-100 GHz frequency range, comprising a polyimide having an imide equivalent weight of 375 or greater. Such elements include circuit substrates, antennas and protective coatings. The polyimide preferably demonstrates a dielectric loss at 12.8 GHz of 0.009 or less. The polyimide preferably has a Tg of 260xc2x0 C. or greater. The polyimide may be cured or crosslinked, as described in co-pending U.S. patent application Ser. No. 09/642,724, filed on even date herewith.
What has not been described in the art, and is provided by the present invention, is a means of enhancing electronic properties of polyimides in the 1-100 GHz frequency range by selecting polyimides of higher imide equivalent weight.
In this application:
xe2x80x9ccuredxe2x80x9d describes a thermally treated polymer having less solubility at a given temperature than the same polymer prior to treatment, preferably measured in regard to solvents methyl ethyl ketone, N-methylpyrrolidone or xcex3-butyrolactone and preferably at room temperature;
xe2x80x9ccrosslinkedxe2x80x9d describes a polymer having a network structure, typically demonstrated by insolublility even at elevated temperatures and for extended times;
xe2x80x9cbenzylic hydrogenxe2x80x9d refers to a hydrogen atom attached to a carbon atom directly attached to an aromatic ring, e.g., any of the three methyl hydrogens of toluene, any of the two alpha hydrogens of ethyl benzene, etc.;
xe2x80x9cpolyimidexe2x80x9d refers to a polyimide polymer unless indicated otherwise;
xe2x80x9ca polyimide comprising a diaminexe2x80x9d and like phrases should be understood to refer to polyimide polymers incorporating segments derived from the indicated diamine monomers, as by a polymerization including said monomers;
xe2x80x9cdiamines comprising pendent fluorenyl groupsxe2x80x9d refers to fluorenyl compounds disubstituted at the 9 position with amine-containing substituents, such as 9,9-bis(aminoaryl)fluorenes;
xe2x80x9cpolyimides comprising pendent fluorenyl groupsxe2x80x9d refers to polyimides derived at least in part from pendent-fluorenyl diamine monomers;
xe2x80x9cC(number)xe2x80x9d refers to a chemical moiety containing the indicated number of carbon atoms; and
the term xe2x80x9csubstitutedxe2x80x9d used without reference to a particular substituent means, for a chemical species, substituted by conventional substituents which do not interfere with the desired product or process, e.g., substituents can be alkyl, alkoxy, aryl, phenyl, halo (F, Cl, Br, I), cyano, etc.
It is an advantage of the present invention to provide materials having good mechanical, optical and electrical characteristics of polyimides and additionally having improved gigahertz performance.